﻿using System;
using System.Collections.Generic;
using System.Text;
using Yitter.IdGenerator;

namespace Util
{
    public class SnowFlakeGenerator
    {
        //机器ID
        private static long workerId=0;
        private static long twepoch = 687888001020L; //唯一时间，这是一个避免重复的随机量，自行设定不要大于当前时间戳
        private static long sequence = 0L;
        private static int workerIdBits = 6; //机器码字节数。4个字节用来保存机器码(定义为Long类型会出现，最大偏移64位，所以左移64位没有意义)
        public static long maxWorkerId = -1L ^ -1L << workerIdBits; //最大机器ID
        private static int sequenceBits = 6; //计数器字节数，10个字节用来保存计数码
        private static int workerIdShift = sequenceBits; //机器码数据左移位数，就是后面计数器占用的位数
        private static int timestampLeftShift = sequenceBits + workerIdBits; //时间戳左移动位数就是机器码和计数器总字节数
        public static long sequenceMask = -1L ^ -1L << sequenceBits; //一微秒内可以产生计数，如果达到该值则等到下一微妙在进行生成
        private long lastTimestamp = -1L;
        /// <summary>
        /// 机器码
        /// </summary>
        /// <param name="workerId"></param>
        public SnowFlakeGenerator(long workerId)
        {
            //if (workerId > maxWorkerId || workerId < 0)
            //    throw new Exception(string.Format("worker Id can't be greater than {0} or less than 0 ", workerId));
            //SnowFlakeGenerator.workerId = workerId;

            var options = new IdGeneratorOptions(1);
            YitIdHelper.SetIdGenerator(options);
        }
        //public long NextId()
        //{
        //    lock (this)
        //    {
        //        long timestamp = timeGen();
        //        if (this.lastTimestamp == timestamp)
        //        { //同一微妙中生成ID
        //            SnowFlakeGenerator.sequence = (SnowFlakeGenerator.sequence + 1) & SnowFlakeGenerator.sequenceMask; //用&运算计算该微秒内产生的计数是否已经到达上限
        //            if (SnowFlakeGenerator.sequence == 0)
        //            {
        //                //一微妙内产生的ID计数已达上限，等待下一微妙
        //                timestamp = tillNextMillis(this.lastTimestamp);
        //            }
        //        }
        //        else
        //        { //不同微秒生成ID
        //            SnowFlakeGenerator.sequence = 0; //计数清0
        //        }
        //        if (timestamp < lastTimestamp)
        //        { //如果当前时间戳比上一次生成ID时时间戳还小，抛出异常，因为不能保证现在生成的ID之前没有生成过
        //            throw new Exception(string.Format("Clock moved backwards.  Refusing to generate id for {0} milliseconds",
        //                this.lastTimestamp - timestamp));
        //        }
        //        this.lastTimestamp = timestamp; //把当前时间戳保存为最后生成ID的时间戳
        //        long nextId = (timestamp - twepoch << timestampLeftShift) | SnowFlakeGenerator.workerId << SnowFlakeGenerator.workerIdShift | SnowFlakeGenerator.sequence;
        //        return nextId;
        //    }
        //}
        public long NextId() 
        {
            return YitIdHelper.NextId();
        }
        /// <summary>
        /// 获取下一微秒时间戳
        /// </summary>
        /// <param name="lastTimestamp"></param>
        /// <returns></returns>
        private long tillNextMillis(long lastTimestamp)
        {
            long timestamp = timeGen();
            while (timestamp <= lastTimestamp)
                timestamp = timeGen();
            return timestamp;
        }
        /// <summary>
        /// 生成当前时间戳
        /// </summary>
        /// <returns></returns>
        private long timeGen()
        {
            return (long)(DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;
        }
    }
    public class Factory
    {
        /**
         * 每一部分占用位数的默认值
         */
        private readonly int DEFAULT_MACHINE_BIT_NUM = 5;   //机器标识占用的位数
        private readonly int DEFAULT_IDC_BIT_NUM = 5;//数据中心占用的位数
        private int machineBitNum;
        private int idcBitNum;
        public Factory()
        {
            this.idcBitNum = DEFAULT_IDC_BIT_NUM;
            this.machineBitNum = DEFAULT_MACHINE_BIT_NUM;
        }
        public Factory(int machineBitNum, int idcBitNum)
        {
            this.idcBitNum = idcBitNum;
            this.machineBitNum = machineBitNum;
        }
        public Util.SnowFlakeGenerator Create(long idcId, long machineId)
        {
            return new SnowFlakeGenerator(machineId);
        }
    }
}
